well, if you're an annon girl, i can understand. it's normal for some women to find cocks ugly, no problem with that. and if the penis isn't clean you will notice a really strong and bitter taste, that leaves an also strong aftertaste. it's something about stuff the penis naturally produces. but all you gotta do is ask the guy to clean his dick before, or you may clean it yourself, he'll love it! ;)
the cum may also be a problem. it may be sweet or a little bitter, or a lot bitter... it depends on the guy and i've heard some foods may change the cum's taste too. if you're not comfortable with drinking it, let he cum on your body/face on far from you. you don't have to do what you don't like.
but, if you're a annon guy... seriously, i don't get you :o